Q5 (10 points)
A commonly used model of the distribution of terms in a collection is Zipf's law. It is stated as, if t_(1) is the most common term in the collection, t_(2) is the next most common, and so on, then the collection frequency cf_(i) of the i-th most common term is proportional to (1)/(i). That is,
cf_i ā (1)/(i)
So if the most frequent term occurs cf_(1) times, then the second most frequent term has half as many occurrences, the third most frequent term a third as many occurrences, and so on. The intuition is that frequency decreases very rapidly with rank.
Equivalently, we can write Zipf's law as cf_(i) = ci^(-1) or as log(cf_(i)) = log(c) + (-1)log(i) where c is a constant (for English, c = 0.1).
If we ignored all occurrences of the five most frequent terms in the collection, what proportion of term occurrences would be removed from the collection?